1. Field of the Invention
This invention relates to a process for polymerization of ethylene and more particularly to a process for efficiently polymerizing ethylene by use of a novel ethylene polymerization catalyst.
2. Description of the Invention
As is known in the art, the material obtained by reacting a magnesium-containing compound used as a carrier, such as a magnesium halide, magnesium alkoxide, etc. with a titanium halide constitutes a component of a highly active catalyst for polymerization of ethylene.
Japanese Patent Publication No. 34098/1971 discloses in detail the use of the reaction product of a magnesium alkoxide and a titanium halide as a catalyst component. With this catalyst component, however, satisfactory catalyst activity and polyethylene of the desired quality are not obtained. Therefore, various methods have been proposed to obtain improved results. For example, Japanese Patent Publication No. 30118/1976 and Japanese Patent Application Laid-open (Kokai) No. 144490/1979 disclose a method in which magnesium alkoxide, after being treated with a halogenating agent, is reacted with a titanium compound, and Japanese Patent Publication No. 30118/1976, Japanese Patent Application Laid-open (Kokai) Nos. 98076/1977 and 2580/1978 disclose a method in which magnesium alkoxide is reacted with a titanium compound in the presence of a halogenating agent, a silicon halide or an electron donating compound. Although these methods increase the catalytic activity, the increased activity is still not sufficiently high.
The ultimate object of the aforedescribed methods which have been proposed for the high activity polymerization of ethylene is to omit the catalyst removing step and to simplify the production steps by improving the catalyst activity and at the same time, to increase the quality of the product obtained. It is, therefore, most desirable to increase the catalyst activity to higher levels. In addition, to facilitate handling of the slurry during production of polyethylene, it is desired that the bulk density of the polymer should be maximized, the particle diameter of the powders polymer should be uniform, and the amount of fine particles and of coarse particles should be reduced.
We have now discovered that a solid component, which is produced by pre-treating a magnesium dialkoxide with a specific amount of silicon compound in the presence of alcohol and then reacting the solid material so obtained with titanium halide in the presence of a silicon compound has greatly increased catalytic activity, and that the polymer produced using this catalyst component has excellent bulk density and powder particle size characteristics.